Analysis and Mitigation of the Feedthrough Capacitance in Weakly Coupled Silicon Resonators

Weakly coupled silicon micromechanical resonators have been widely studied for sensors. However, parasitic feedthrough capacitances degrade the magnitude of output signals. This article presents a detailed investigation on the influence of the feedthrough capacitance, in particular, at low air pressures. It begins with a theoretical analysis and simulation using an equivalent circuit model to explore the impact of feedthrough capacitance on the output current of the coupled resonators. Experimental tests are conducted to illustrate the effects of feedthrough capacitance at different air pressures. The results reveal that resonators with lower quality factors are more susceptible to feedthrough influence. Using a half-frequency driving method, the feedthrough signal is effectively suppressed at low air pressures. The experiments show that it significantly suppresses the feedthrough level to -93 dB and achieves a 13 dB signal acquisition even under an air pressure of 120 Pa.